The invention relates to fabrication of circuits and circuit elements, and more particularly to deposition techniques using aperture masks.
Circuits include combinations of resistors, diodes, capacitors and transistors linked together by electrical connections. Thin film integrated circuits include a number of layers such as metal layers, dielectric layers, and active layers typically formed by a semiconductor material such as silicon. Typically, thin film circuit elements and thin film integrated circuits are created by depositing various layers of material and then patterning the layers using photolithography in an additive or subtractive process which can include a chemical etching step to define various circuit components. Additionally, aperture masks have been used to deposit a patterned layer without an etching step or any photolithography.
In general, the invention is directed to deposition techniques using aperture mask patterns formed in one or more elongated webs of flexible film. The techniques involve sequentially depositing material through aperture mask patterns formed in the webs to define layers, or portions of layers, of a circuit. A deposition substrate can also be formed from an elongated web, and the deposition substrate web can be fed through a series of deposition stations. Each deposition station may have its own elongated web formed with aperture mask patterns. In some embodiments, each elongated web of aperture mask patterns travels in a direction perpendicular to the deposition substrate web. In this manner, the circuit fabrication process can be performed in-line. Moreover, the process can be automated to reduce human error and increase throughput.
In some embodiments, circuits can be created solely using aperture mask deposition techniques, without requiring any of the etching or photolithography steps typically used to form integrated circuit patterns. Aperture mask deposition techniques can be particularly useful in fabricating circuit elements for low-cost integrated circuits such as radio frequency identification (RFID) circuits or for fabricating circuits for electronic displays such as liquid crystal displays or organic light emitting diode displays. In addition, the techniques can be advantageous in the fabrication of integrated circuits incorporating organic semiconductors, which typically are not compatible with etching processes or photolithography.
In one embodiment, the invention is directed to an aperture mask comprising an elongated web of flexible film, and a deposition mask pattern formed in the film, wherein the deposition mask pattern defines deposition apertures that extend through the film. The elongated web may be greater than approximately 50 centimeters or greater than approximately 100 centimeters or greater than approximately 10 meters, or greater than approximately 100 meters in length. The mask can be sufficiently flexible such that it can be wound into a roll without damage or forming a permanent bend. Also, the aperture mask may be reusable. Aperture masks in this form can be used as part of an in-line deposition system.
In other embodiments, the invention is directed to in-line deposition systems and in-line deposition methods. For example, a system may include a first web of flexible film and a second web of flexible film, wherein the second web of film defines a deposition mask pattern. The system may also include a drive mechanism that moves at least one of the first and second webs relative to the other of the first and second webs, and a deposition unit that deposits onto the first web of film through the deposition mask pattern defined by the second web of film. Various in-line deposition methods are also described.
In additional embodiments, the invention is directed to a stretching apparatus for aligning a deposition mask pattern with a substrate in an in-line deposition system. For example, the apparatus may include a first stretching mechanism to stretch the first web of film in a down-web direction, a cross-web direction, or both directions in order to align the deposition mask pattern formed in the first web of film with a deposition substrate. The deposition substrate may also form a web, or alternatively may be a conveyance web carrying a series of substrates. The second web of film may also be stretched in the down-web direction, cross-web direction, or both directions.
The various embodiments of the invention can provide one or more advantages. For example, the invention can facilitate the fabrication of relatively small circuit elements using aperture mask deposition techniques. For example, the invention can facilitate fabrication of circuit elements having widths less than approximately 1000 microns, less than approximately 50 microns, less than approximately 20 microns, less than approximately 10 microns, or even less than approximately 5 microns. In addition, the invention can reduce costs associated with circuit fabrication. Specifically, by streamlining the circuit fabrication process such that deposition can be performed in-line, circuits may be created more quickly and with a reduced number of handling steps. Moreover, by reducing human error, an automated process may produce more reliable circuits than other processes. In this manner, an in-line process can promote increased yields.
Also, because the elongated web may be formed from polymeric material, the aperture masks in the web can be created using laser ablation techniques. Laser ablation techniques may be faster and less expensive than other mask creation techniques. Also, inexpensive polymeric materials can allow the elongated web of masks to be disposable. Laser ablation techniques allow for the fabrication of small deposition apertures, i.e., with widths less than approximately 1000 microns, less than approximately 50 microns, less than approximately 20 microns, 10 microns, or even 5 microns. In addition, laser ablation techniques allow for the creation of deposition apertures separated by a small gap, i.e., less than approximately 1000 microns, less than approximately 50 microns, less than approximately 20 microns, or even less than approximately 10 microns. These small deposition apertures and small gaps can facilitate the fabrication of small circuit elements. Additionally, laser ablation techniques can facilitate the fabrication of aperture mask patterns over large surface areas allowing large area circuits or widely spaced circuit elements to be fabricated.
Another advantage is that the polymeric material that makes up the web of aperture masks may be well suited to be impregnated with magnetic material. In that case, the magnetic material may be used to reduce sag during the in-line deposition process, e.g., by application of attractive or repulsive magnetic force. Furthermore, polymeric material is often stretchable, which allows the mask to be stretched in order to better align the mask with the deposition substrate and possibly to control sag. Stretching techniques in the down-web direction, the cross-web direction, or both may be used to achieve quick and precise alignment of the elongated web of aperture masks relative to the elongated web of deposition substrate material.
Details of these and other embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will become apparent from the description and drawings, and from the claims.